The present invention relates generally to the formation of dielectric layers during fabrication of integrated circuits on semiconductor wafers and specifically to methods for providing dielectric films having low dielectric constants.
The manufacture of integrated circuits involves procedures for forming thin films and layers of various materials on wafers of base semiconductor material and selectively removing areas of such films to provide structures and circuitry. Doped silicon is a typical base wafer material used.
Many procedures for forming thin films on semiconductor substrates involve the chemical reaction of gases to form the films. Such a deposition process is referred to as chemical vapor deposition (xe2x80x9cCVDxe2x80x9d). Conventional thermal CVD processes supply reactive gases to the substrate surface where heat-induced chemical reactions take place to produce a desired film. Plasma enhanced CVD techniques (xe2x80x9cPECVDxe2x80x9d), on the other hand, promote excitation and/or dissociation of the reactant gases by the application of radio frequency (xe2x80x9cRFxe2x80x9d) or microwave energy. The high reactivity of the released species reduces the energy required for a chemical reaction to take place, and thus lowers the required temperature for such PECVD processes.
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Today""s fabrication plants are routinely producing devices having 0.25 xcexcm and even 0.18 xcexcm feature devices, and tomorrow""s plants will be producing devices having even smaller geometries. In order to further reduce the size of the devices on integrated circuits, it has become necessary to use conductive materials having low resistivity and insulators having low dielectric constants. Low dielectric constant films are desirable for premetal dielectric (xe2x80x9cPMDxe2x80x9d) layers and intermetal dielectric (xe2x80x9cIMDxe2x80x9d) layers to reduce the RC delay time of the interconnect metalization, to prevent cross-talk between the different levels of metalization and to reduce device power consumption.
Undoped silicon oxide films deposited using conventional CVD techniques may have a dielectric constant (xe2x80x9ckxe2x80x9d) as low as about 4.0 or 4.2. One approach to obtain a lower dielectric constant is to incorporate other elements in with the silicon oxide film, e.g., fluorine to form doped silicon with fluorine. Fluorine-doped silicone oxide films (also referred to as fluorine silicate glass or xe2x80x9cFSGxe2x80x9d films) may have a dielectric constant as low as about 3.4 or 3.6. Despite this improvement in the dielectric constant, films having even lower dielectric constants are highly desirable for the manufacture of integrated circuits using geometries of 0.18 xcexcm and smaller. Numerous films have been developed in attempts to meet these needs including various carbon-based dielectric layers, such as parylene and amorphous fluorinated carbon. While the above types of dielectric films are useful for some applications, manufacturers are always seeking new and improved methods of decreasing dielectric constants still farther.
An embodiment of the present invention provides methods for forming a carbon-containing layer having a low dielectric constant and good gap-fill capabilities. The method includes depositing a carbon-containing layer on a substrate and transforming the carbon-containing layer to remove at least some of the carbon.
The transforming step may include annealing the carbon-containing layer in a furnace containing a hydrogen atmosphere, for example.
The carbon-containing layer may be a carbon-doped silicon oxide material, where the transforming step changes the carbon-doped silicon oxide.
Additionally, the method may include subjecting the annealed layer to a hydrogen and/or low oxygen plasma treatment to further remove carbon from the layer.
Additionally, a step of adding a capping layer to the annealed, plasma treated material is provided.
Products made by the above methods are also included, such as a product including a low k carbon-containing layer where the low k carbon-containing layer has been transformed to remove some of the carbon from the layer. An additional product includes a transformed carbon-containing layer further subjected to a hydrogen plasma treatment to remove more carbon from the layer. Further, a capping layer deposited over the transformed and hydrogen plasma treated layer is provided.
According to the present invention, a stacked layer structure is provided, which includes a transformed and/or plasma treated low k layer deposited on a substrate and a capping layer deposited on top of the low k material.